There are around 100,000 tree species across the world. Although the majority of these species are in a tropical environment, trees can be found throughout almost any region of the world: in fact, trees number 25% of all plant life. The various species of trees can be divided into many different categories, such as forest species, evergreen species or endangered species.
A plant must possess several characteristics in order to be categorized as a species of a tree. Most experts agree that trees are perennial, meaning that they live for at least two years. Trees are also typically a woody plant, and many scientists claim that trees will have a clearly defined trunk with branches.
The earliest tree species that still exist today are tree ferns. These trees can survive in both tropical and subtropical environments. They are often found in rainforests, along with certain regions of Australia and the South Pacific islands.
The are over 100 kinds of tropical tree species, with the Arecaceae, more commonly known as the palm tree, being one of the most well-known. Most palm trees require a low, wet region to thrive, but there are 130 lesser-known palm species that grow outside the tropical regions. Although palm trees have a minimalist appearance, they have been used for many purposes throughout history, from practical resources to spiritual rituals.
The classification "evergreen" means that these trees keep their green leaves all year, never falling into traditional seasonal patterns. Evergreen tree species tend to flourish in even the harshest environments. Pine trees might be found in warm ocean-front settings, but they can also bear through long freezing winters in northern America and Canada. Although pine trees and other evergreens can survive despite drastic temperature fluctuations, they do usually need an acidic soil to grow in.
Deciduous trees are the opposite of the evergreen. These trees have a yearly pattern of color-changing leaves, bare branches, flowering buds, and leafy green life. Deciduous literally means "that which falls off." Leaves might start falling off at the onset of cold weather or as the atmosphere begins to dry up. Some deciduous tree species include birches, oaks or poplars.
Several species of trees have made it to the endangered list. The Bois Dentelle is the rarest tree species alive. There are only two Bois Dentelles still standing, both growing in Mauritius. These trees have bell-shaped flowers with petals resembling lace. Although experts have not decided on a reason for their decline, most do not believe that their endangerment is the result of any human actions.